|
曝光台 注意防骗 网曝天猫店富美金盛家居专营店坑蒙拐骗欺诈消费者
7. Roll-Lateral Experiment
Background
In flight simulation, the roll and lateral translational degrees of freedom are treated together for several reasons. First, owing to the motion platform geometry, a certain amount of lateral translational motion must accompany a rolling motion to locate the center of rotation properly. Second, for coordinated maneuvers, in which the body-axis lateral aero-propulsive forces are zero, lateral translational platform motion provides an acceleration to counteract the “leans” that would result from only rolling the cockpit.
Figure 69 shows a coordinated and an extremely uncoordinated case (roll only) with a pendulum hanging from the top of a rolling flight simulator cockpit. In both cases, altitude remains constant. In the coordinated case, the platform moves laterally with an acceleration of g*tanφ plat; however, the body-axis lateral component of the aero-propulsive force is zero which keeps ay = 0. Sustaining the platform acceleration to maintain this coordination consumes available lateral displacement quickly.
Coordinated Uncoordinated
φ plat
φ plat
Lift
Yplat = gtanφ plat Yplat = 0
a = 0
y
g = –gsinφ platCockpit
Figure 69. Coordinated vs. uncoordinated flight.
Most motion-base flight simulators are hexapods with similar displacement capabilities. In these devices, sufficient lateral translational platform travel is not available to simulate exactly the motion cues that a pilot would receive in coordinated flight. To reduce the amount of lateral displacement used, platform drive commands use several methods. In one method, the roll angle of the motion platform is reduced relative to the model (and thus the visual scene). This requires less lateral travel, since less lean-due-to-roll motion is present. In the second method, less than the full amount of lateral translational motion required for coordination is used. The purpose of his study was to investigate the trade-off between these two options.
Experimental Setup
Task
Constant-altitude lateral side steps were performed between two points 20 ft apart. A positioning sight in the visual scene allowed pilots to use parallax to determine their positioning error precisely. The desired positioning performance standard was ±3 ft about the desired hover point (which was 20 ft away), and the adequate perfor-mance standard was ±8 ft. The task had to be completed in less than 10 sec for desired performance and in less than 15 sec for adequate performance. Pilots pressed an event marker on the center stick when they felt they had acquired the station-keeping point. They were instructed that push-ing this button meant that they were within the position error for desired performance, and that they believed they would remain within the desired performance standard.
Simulated Vehicle Math Model
The math model had only two degrees of freedom. Altitude remained constant at 25 ft; heading, pitch, and longitudinal position remained constant at zero. Pilots controlled the vehicle with lateral displacements of a center stick only. The equations for motion were
直升机网 www.helicopter.cn
直升机翻译 www.aviation.cn
本文链接地址：Helicopter Flight Simulation Motion Platform Requirements(49)
| 
